<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS选择器-伪类选择器-4</title>
    <style>
        .container{
            border: 1px solid red;
        }
        .container:before{
            content: "谁的前面呢?";
        }
        .container:after{
            content: "谁的后面呢";
        }
    </style>
</head>
<body>
<div class="container">
    <p>这是一个段落!</p>
</div>
</body>
</html>